There was a comment that says that the +16 is only in air and when in water it becomes more a +5.... anybody here know what Slipperydick as talking about?

it's the different refraction properties of air and water. the +16 is rated in air and loses it's 'power' when in water. the +16 and other similarly constructed lens have 2 elements with air sealed in between. A 'true' underwater +10 or +5 like the subsee and macromate have 4 elements i believe which means the lens does not lose it's power underwater. It's the same power on land and underwater.

Slipperdick aka keri wilk's explanation is pretty clear. why not post there for further explanation if you need?

yes you can. i just used it with the 60mm. the downside is that you get a little less magnification compared to using the 100mm. with the subsee you have to be really close to get max magnification. probably almost touching the subject